Refrigeration systems



Dec. 12, 1961 N. ANDERSON REFRIGERATION SYSTEMS Filed Jan. 26, 1959 FIG.2.

INVENTOR A a/(MAN 4/vokso/v ATTO R N EY United States Patcffif 3,012,413REFRIGERATION SYSTEMS Norman Anderson, Hanworth, England, assignor toSir George Godfrey & Partners (Holdings) Limited, Hanworth, England 7Filed Jan. 26, 1959, Ser. No. 789,014 Claims priority, application GreatBritain Jan. 25, '1958 2 Claims. (Cl. 62-272) This invention relates torefrigeration systems and is 0 more particularly, though notexclusively, concerned with systems operating on the air-cycle principleas used, for example, for cooling the cabins of aircraft. The object ofthe invention is to provide means to overcome the difliculties caused byice formation in refrigeration systems generally and which may haveparticularly serious effects in the case of airborne systems supplyingcooled air to aircraft cabins, and also systems in which suchdifliculties are substantially overcome.

In air-cycle refrigeration systems of the type used for cooling aircraftcabins pressure air for supply to the cabin is expanded across theturbine of arr air-cycle refrigerator, consisting of a turbine drivingacompressor or fan mount-j ed on a common shaft with the turbineyto dowork ant? thereby loseheat, such pressure air. eitherrpassingdirectly 25through t'h'e'tu'rbinejwith the compressor or fan'operating in free airmerely .t'i'constitute an atmospheric brake or servinglto draw airacross an air-.to-air .heat exchanger through which the'pressure airpasses on its way to the turbine, or passing first through thecompressor and then through a heat exchanger before being expandedacross the turbine with further loss of heat.

Systems of the foregoing type usually have a water extractor inserted inthe air duct near the downstream end of the system so that Water isremoved immediately before the air enters the cabin, and the maindifliculty which has been experienced under icing conditions is blockageof the water extractor which seriously impedes the air flow to the cabinand gives rise to high pressures in the duct. The trouble originateswith frost formation in the water extractor but in addition, whenthawing takes place, slush which has collected in the duct upstream ofthe water extractor is blown into the latter causing even more severeblockage.

According to the invention means for overcoming these difliculties takethe form of an ice guard adapted for connection in a duct of arefrigeration system circuit and comprising a foraminous element of suchsmall hole size that the least frost deposit thereon causes considerableblockage of the duct and builds up a pressure therein to compress therefrigerant to produce self heating of the refrigerant and so maintain adelivery temperature above the freezing point of water, the total areaof the element being so chosen that an acceptable pressure drop acrossthe element is obtained when the element is free of frost deposit.

The invention also includes a refrigeration system wherein there isconnected in circuit a foraminous element having the abovecharacteristics.

The foraminous element provides a simple and effective ice guard and itpreferably comprises a metal gauze of very fine mesh in order to ensurethat the smallest degree of frost deposit thereon causes blockage. Ifdesired the gauze may be backed with a perforated plate in order to giveit the required mechanical strength to resist rupture under the highpressure drop which obtains during frosting.

When applied to an air-cycle refrigeration system the foraminous elementis preferably placed immediately downstream of the turbine of theaircycle refrigerator in order to limit the length of air duct at highpressure and to avoid effects due to heat transfer into the ducting.

The invention will now be further described with refer; ence to theaccompanying drawings which illustrate, by way of example, one way ofcarrying the invention into eftectin connection with an airborneair-cycle refrigeration system for supplying cooled air to an aircraftcabin, and in which FIGURE 1 is a diagrammatic flow diagram of thesystem, and

FIGURE 2 is a cross-sectional view of an ice guard of the systemaccording to the invention.

In the circuit of FIGURE 1 charge air for pressurizing and ventilatingthe cabin is obtained from a tapping 1 of the compressor of a gasturbine engine of the aircraft. Air from this tapping passes along aduct 2 through an air-toair primary heat exchanger 3 which reduces itstemperature, and thence through a duct 4 to a valve 5. As thetemperature of the charge air leaving the primary heat exchanger 3 isusually still too high it is brought to an acceptable level by expandingthe air across the turbine of a cold air unit 6 in the form of aturbo-compressor.

The turbo-compressor has an inward-flow radial turbine 7 driving acentrifugal compressor 8 on a common shaft. Charge air passesfrom thevalve 5 through the compressor 8, through a duct 9 to a secondaryair-to-air heat exchanger 10, through. a duct 11 to the turbine 7 acrosswhich it is expanded and into a cabin supply duct12. During passage ofthe charge air through the turbo-compressor it is compressed and heatedby the compressor 8, heat then being removed in the secondary heatexchanger 10 after which it is expanded across the turbine 7 whichdrives the compressor 8 and consequently removes energy from the chargeair to cool the latter.

An ice guard 13 is located in the supply duct 12 immediately downstreamof the turbine 7 between the latter and a water extractor 14 inserted inthe duct 12 before its entry into the aircraft cabin, the cabin wallbeing shown diagrammatically at 15. A non-return valve 16 is located inthe duct 12 immediately before its entry into the cabin.

Referring more particularly to FIGURE 2, the ice guard 13 comprises atubular body 17 of double-conical form having coaxial inlet and outletconnections, 18 and 19 respectively, by means of which it is connectedinto the supply duct 12. The double-conical form of the body 17 resultsfrom the assembly together of inlet and outlet body portions, 20 and 21respectively, each of outwardly flared form and radially flanged attheir wider ends 20a and 21a so that when connected by means of a ringof bolts such as 22 pasing through the mating flanges an airtightassembly results.

To ensure the foregoing airtight assembly, the flange 20a on the inletportion 20 of the body is turned axially at its radially outer edge 20bin order to embrace the thicker radial flange 21a of the outlet portion21. The periphery of the flange 21a is grooved to receive a sealing ring23 which seals against the inner surface of the axially turned portion20b of the inlet body portion 20. Sandwiched between the radial faces ofthe flanges 20a and 21a is a foraminous element 24 comprising a metallicgauze of a very fine mesh, or a plurality of such metallic gauzessuperimposed one upon the other. At the outlet or delivery side of thegauze or gauzes a perforated metal backing plate 25 is arranged, suchplate also being sandwiched at its periphery between the flanges 29a and21a.

The foraminous element 24 constitutes a simple and effective ice guard,its hole size being such that the least frost deposit thereon causesconsiderable blockage of the duct 12 and builds up a pressure therein,such pressure rise compressing the air to produce self heating of thecharge air upstream of the ice guard 13 to maintain a deliverytemperature above the freezing point of water.

Patented Dec. 12, 1961 The total area of the foraminous element 24 is sochosen that an acceptable pressure drop across the element is obtainedwhen the latter is free of frost deposit.

The water extractor 14 removes water present in the charge air afterleaving the ice guard 13, and due to the latter it has been found inpractice that the charge an entering the water extractor 14 containsonly water and not slush or ice. For his reason the water extractor 14need not embody the usual relief valve, as a result of which it canbe-made of more simple and efficient design.

For heating purposes air is taken from the tapping 1 along a duct 26,through the valve 5, a flow controller 27 and a duct 28 which feeds intothe supply duct 12'immediately upstream of the Water extractor 14. Forfull cooling the only charge air entering the supply duct 12 passedthrough the heat exchanger 3, valve 5 and turbo-compressor 6, whereasfor full heating all this charge air passes through the valve 5 and flowcontroller 27. A Thus the valve 5 acts, in efiect, as a mixing valve andits S'ZttlHg dGiEI- mines the degree of cooling and/or heating of thetotal charge air entering the cabin.

The main flow of the cooled air is limited by the r102 zles of theturbine 7, and the flow controller 27 controls the subsidiary flow ofhot air in dependence upon the supply pressure to the cabin. 7

When the aircraft isfly'ing, cooling air for the primary and secondaryheat exchanges 3 and 10 is obtained by ram efieet, but when the systemis used on the ground it necessary to induce a flow of cooling airisobtained by opening normally closed valves 29 Opening these valvessupplies air under pressure from the tapping 1 to galleries 30associated respectively with the heat exchanges 3 and 10, and thepressure air is ejected from these galleries to provide a jet pumpefiect' which induces a flow of cooling air over' the heat exchangers.

1. A ventilating system having means for supplying comparatively warmair and incorporating a refrigeration system having a circuit includinga turbo-compressor unit comprising a turbine and a compressor, a heatexchanger arranged in the circuit between said turbine and saidcompressor; an ice guard arranged in the circuit downstream of saidcompressor and comprising in combination a foraminous element of suchsmall hole size that frost deposit thereon causes considerable blockageof the duct resulting in a pressure rise therein which compresses therefrigerant upstream of the element to produce self-heating of therefrigerant and maintain a delivery temperature in the duct above thefreezing point of water, two generally f'rustoconical body portionarranged with their wider ends adjacent each other and provided withsubstantially coaxial inlet and outlet connectionsat their narrowerends, and a perforated plate, which backs said element and with saidplate is sandwiched between said wider ends of the body portions; saidcircuit of the refrigeration system also including a water extractorupstream of which said ice guard is placed and means for mixingrefrigerated air with said comparatively warm air at a point in thecircuit between said element and said water extractor.

2. A ventilating'syster'n according to claim 1 wherein said foraminouselenlent comprises a fiat sheet of metal gauze of very fine mesh.

References- Cited indie file or this atent

